What is the most appropriate next investigation for a boy with a history of eczema presenting with cough and wheezing following an upper respiratory tract infection (URTI)?

Spirometry with Bronchodilator Response Testing

In this boy with eczema, recurrent cough, and wheezing following a URTI, spirometry with bronchodilator reversibility testing is the most appropriate next investigation to objectively confirm asthma before initiating treatment. 1, 2

Why Objective Testing is Essential

• Asthma should NOT be diagnosed based on symptoms alone, even when classic features like recurrent wheeze and atopy (eczema) are present—this is a strong recommendation from the European Respiratory Society. 1, 2
• This child has high-risk features for persistent asthma (eczema plus wheezing), but diagnosis still requires at least two abnormal objective tests, not just clinical suspicion. 2
• Recurrent wheeze is the most important symptom of asthma, not isolated cough, and this child has documented wheezing, making asthma a strong diagnostic consideration. 1, 3

Spirometry as First-Line Investigation

• Spirometry is recommended as the first-line objective test for children aged 5-16 years under investigation for asthma, and most children in this age range can successfully perform acceptable spirometry. 2, 4
• Bronchodilator reversibility (BDR) testing showing ≥12% improvement in FEV1 after bronchodilator is a key diagnostic test for asthma. 2
• Testing is most useful when the child is symptomatic or when wheezing is present, as spirometry is frequently normal during stable disease. 2

Additional Diagnostic Considerations

• If spirometry and BDR testing are performed, fractional exhaled nitric oxide (FeNO) testing should be considered as a second objective test, as elevated levels suggest eosinophilic airway inflammation. 2
• Asthma should only be diagnosed when two or more recommended diagnostic tests (spirometry, BDR, FeNO) are abnormal. 2
• In patients suspected of having cough-variant asthma but with nondiagnostic physical examination and spirometry, methacholine inhalation challenge testing should be performed to confirm bronchial hyperresponsiveness. 1

Important Clinical Pitfalls to Avoid

• Do not assume cough always represents asthma—children with chronic cough (>4 weeks) as the only symptom are unlikely to have asthma and should be investigated according to chronic cough guidelines. 1, 3, 5
• However, this child has both cough AND wheezing with recurrent episodes, making asthma more likely than isolated chronic cough. 1, 3
• Do not initiate empiric treatment with inhaled corticosteroids or bronchodilators without objective confirmation, as symptom improvement after preventer medication alone should not be used to diagnose asthma. 1, 2

Age-Specific Considerations

• If this child is under 5 years old, spirometry may not be feasible, and the diagnostic approach differs significantly—alternative techniques such as interrupter resistance or oscillometry may be considered, though evidence is limited. 6
• For preschool children, a careful therapeutic trial with close monitoring may be appropriate if objective testing cannot be performed, but treatment should be stopped if no clear benefit is seen within 4-6 weeks. 3